The Smiths consider a computer which is commonly considered a great help in their work

问题补充：

The Smiths consider a computer, which is commonly considered a great help in their work and study.

A. to buy; to be

B. buying; to be

C. to buy; being

D. buying; being

答案：

A. to buy; to be

(答案→)B. buying; to be

C. to buy; being

D. buying; being

解析：考查短语：考虑做某事consider doing sth，被认为，be considered to be，句意：史密斯一家考虑买一台电脑，普遍被认为在他们的工作和学习中非常有帮助。所以选B。